Cryptographic instrument



A. F. MICHELSQN CRYPTOGRAPHIC INSTRUMENT 1mm, W68

2 Sheets-Sheet 1 Filed May 5, 1966 jaw. .23, was A. F. MICHELSOM CRYPTOGRAPHIC INSTRUMENT 2 Sheets-Sheet 2 Filed May 6, 1966 Unit 3,364,595 Patented Jan. 23, 1968 3,3645% CRYPTCGRAPHKC INSTRUMENT August F. Michelson, 912 Chicago Ave, Minneapolis, Minn. 55404 Filed May 5, 1966, Ser. No. 547,804 8 Claims. (Cl. 35--2) ABSTRACT OF THE DESCLUSURE A cryptographic instrument having a pair of disc means including first and second discs which are rotatably mounted on a base plate, and being adapted to encipher and decipher a message. The first disc has a plurality of pins mounted thereon at selected positions about the periphery, and the second disc has a plurality of teeth thereon sequentially engageable by the pins whereby the second disc will be incrementally rotated by the pins as the first disc means is rotated. Thus, by selective engagement of the various pins in the first disc, a substantial number of initial key positions and primary code keys are possible.

This invention relates to the art of cryptography, and, more particularly, to a cryptographic instrument for enciphering and deciphering messages in a novel and highly versatile manner.

One object of the present invention is to provide a cryptographic instrument which, although simple in construction and operation, can be used to transpose messages into and out of an almost unlimited number of codes and in which a change from one code to another can be quickly and easily accomplished. In the illustrated embodiment of the present instrument, for example, any combination of the twenty six letters of the Roman alphabet including words or names in any language, or even non-word combinations or single letters, may be used as the primary code key. In addition, there are 17,576 possible initial key positions of the parts of the illustrated embodiment so that the size of the number of possible codes is enormous. However, with knowledge of the primary code key and the starting key position, enciphering and deciphering become quite simple. Even more complications may be built into the code scheme chosen to be used and examples of these will be discussed hereinafter.

Another object of the present invention is to provide a cryptographic instrument for translating a message into code using different ciphers for representing the same character in the clear text. Thus the code cannot be broken by ordinary cryptographic techniques. For example, skillful cryptographers are aware of the frequency of appearance of certain letters of the alphabet in a particular language and can readily identify these letters when the' same cipher is used to represent them at each occurrence. With different ciphers, this technique is not applicable.

Still another object of this invention is to provide a mechanical cryptographic instrument which is simple and inexpensive in its construction, requiring only a few easily produced parts which can be quickly assembled.

Another object of this invention to provide a cryptographic instrument having the aforementioned characteristics but which is relatively easy to use. In this respect, proper use of the instrument requires only the memorization or recording of a few factors and once the instrument is correctly set up, translation thereafter follows easily and without mental effort.

The above objectives are accomplished in the present invention by means of a unique combination of coding elements. Briefly described, the instrument includes three coding discs, one being termed a character disc and having indicia thereon representative of the letters or characters in the clear test and the other two being termed cipher discs, these discs carrying symbols or indicia for constituting the coded message. Each of the characters on the character disc has associated with it a pin which is movably mounted so as to protrude selectively to opposite sides of the character disc, the primary code key determining the direction in which these pins protrude. Each of the symbols on the cipher discs has a tooth associated therewith and the cipher discs are mounted so that the cipher disc teeth may be disposed in the path of travel of the pins on the character disc as that disc is rotated. The cipher discs are disposed on opposite sides of the character disc so that pins protruding on one side can advance one cipher disc and pins protruding on the other side can advance the other cipher disc. The initial position of the three discs is determined by a secondary key. Each character of the clear text is thus represented by two ciphers, and the code scheme used is therefore termed a dual-cipher system.

Other objects, advantages and new features of this invention will become apparent from a consideration of the following detailed description of a preferred embodiment thereof, when read in conjunction with the accompanying drawings in which:

FIGURE 1 is a plan view of the instrument, partially in section on the line 1-1 of FIGURE 2;

FIGURE 2 is a section taken on line 2--2 of FIGURE 1; and

FIGURES 3 to 8 are plan views on a reduced scale, showing the positions of the parts for each of the characters in an exemplary message.

A preferred embodiment of the present invention is generally indicated by the reference numeral 10 throughout the several views of the drawing. Instrument 10 includes a base plate 12 on which are rotatably mounted a character disc 14 and two cipher discs 16 and 18 in a manner to be subsequently described. Base plate 12 carries a plurality of support feet 20 and has a recess 22 formed therein, so that the user may freely insert his finger beneath the character disc 14 when adjusting the device.

Character disc 14 is mounted for rotation about a fixed shaft 24. A spacer 26 defines the axial position of character disc 14 on shaft 24 and also provides a friction surface at the interface 28 between these parts so that character disc 14 will not spin freely when rotated. A cap 30 frictionally received at the outer end of shaft 24 retains character disc 14 in place. Shaft 24 may be mounted in any desired manner, but preferably is provided with a flange 32, the spacer 26 having a suitably shaped counterbore for receiving the flange 32 and the adjacent portion of shaft 24 and being attached to base plate 12, by means of an adhesive for example, to confine the flange 32 and hold the shaft securely in place.

Disposed in an arcuate array around the periphery of character disc 14 are twenty-six pins 34 each of which is mounted with a snug fit in a suitable aperture 36 in character disc 1d. As seen best in FIGURE 2, pins 34 are longer than the thickness of character disc 14 so that they may protrude to either side thereof, the snug fit retaining them in their selected positions. Of course, the invention is not limited to this number of pins. As shown, the charactors of the Roman alphabet are printed or otherwise reproduced as indicia adjacent each of the pins 34.

Considering now the cipher discs 16 and 18, these discs are mounted for rotation about a common axis on a flanged shaft 38 fixedly secured in a spacer 40, in the same way that shaft 24 is secured in spacer 26. Cipher disc 18 is mounted adjacent spacer 40 and is retained there by means of a flanged spacer sleeve 42 which is fixed on shaft 38. Cipher disc 16 is then mounted adjacent spacer sleeve 42 and is held in place by a cap 44 similar to cap 3i). As with spacer 26, the relatively large areas of spacer 4t) and spacer sleeve 42 in abutment with the discs 16 and 18 provide sufiicient friction to prevent free spinning of these discs, thus making the instrument quite positive in its operation.

Cipher discs 16 and 18 each have a plurality of peripheral projections or teeth, 46 and 48 respectively, in the nature of star wheel teeth. The spacing of shafts Z4 and 38 is such that when the parts are assembled, the teeth 46 and 48 will overlap the periphery of character disc 14 and will thus lie in the paths of travel of the pins 34 on opposite sides of the character disc. Pins 34 projecting in one direction will therefore engage teeth 46 to advance cipher disc 16 in stepped or incremental fashion and pins 3 projecting in the other direction will similarly advance cipher disc 18 one step for each pin projecting in that direction. There is a tooth, 46 or 48, corresponding to each pin 34-.

Each of teeth 48 is labeled with a symbol placed near the peripheral edge of cipher disc 18. Again the Roman alphabet has been employed but it will be understood that any other symbols or ciphers could be chosen for this indicia. To enable the indicia on cipher disc 18 to be read, cipher disc 16 is provided with an annular peripheral portion 50 of transparent material. Indicia, again Roman characters, for each of teeth 46 are placed on cipher disc 16 within the inner radius of annular portion 54) so that, in effect, two rows of indicia are observable from above cipher disc 16.

In use, the sender and the recipient of a coded message would each be provided with identical instruments 1%. Each would also know the primary key and the secondary key which establishes respectively the directions of protrusion of each of pins 34- and the initial positions of the character disc 14 and the cipher discs 16 and 18.

As stated above, any one of the characters on character disc 14 or any combination thereof may be employed as the primary key. By way of example, the inventors name MICHELSON is used here and the procedure for putting this key into instrument is as follows. First, all pins 34 are pressed to one side of character disc 14 to erase any previous key that may have been employed.

The pins 34 adjacent each character in the new key are then pressed so as to protrude to the other side of character disc 14. The resulting arrangement is illustrated in FIGURE 1 where it will be seen that the pins adjacent the letters M,I,C,H,E,L,S,O and N are pressed toward base plate 12 and are thus not hatched since they are not cut by the section line 1-1 of FIGURE 2. Both the sender and the receiver would set the primary key into their instruments 1b in identical fashion, beginning with the pins protruding in a direction known to both of them. This step may be aided by the recess 22, which allows the user to insert his finger under disc 14 to move pins upward.

The secondary key is any three-letter combination of the characters on the three discs and has been chosen for purposes of the present example as the word KEY. To set this key in the illustrated embodiment, caps 30 and 44 are first removed to permit removal of cipher disc 16 and character disc 14. Cipher disc 18 is then rotated until the character E appears at the six oclock position as seen in FIGURE 1. Character disc 14 is then placed in position with the character Y at the twelve oclock position as shown, immediately adjacent the character E on cipher disc 18. Cipher disc 16 is finally put in place with character K disposed above character E on cipher disc 18 as shown in FIGURE 1.

Having set up his instrument 10 in the manner just described, the sender can then proceed to encipher his message, and this is accomplished by first rotating character disc 14 clockwise from the initial position until the first character of the clear text appears at the twelve oclock position. The cipher representing this character will then appear as the adjacent two characters on cipher discs 16 and 18. The sender then continues to rotate character disc 14 to bring each character of the clear text sequentially into the twelve oclock position. The coding action of the instrument 1% as this process is carried out will probably be best understood by considering the specific example represented in FIGURES 3 to 8 where the six positions of the parts for the clear message MEET ME are shown.

Considering the initial position of the parts as shown in FTGURE 1, it will be noted that clockwise rotation of character disc 14 in bringing the M to the twelve oclock position will cause nine up pins 34, particularly the Y, Z, A, B, D, F, G, J and K pins, and five down pins, the C, E, H, I and L pins, to pass the twelve oclock position. Thus, during this movement, cipher disc 16 will be advanced nine space and cipher disc 18 will be ad vanced five spaces from their respective starting positions. The result is as shown in FIGURE 3, with the characters T and I adjacent the M. The cipher representing the first M in the exemplary message is therefore TI.

Reckoning from the M to the E on character disc 14, there are thirteen up pins 34 and five down pins. Continued clockwise rotation of the character disc will thus advance cipher disc 16 thirteen spaces to the G, and cipher disc 18 five spaces to the O thereon, the final position being shown in FIGURE 4. The remaining characters in the clear text are similarly enciphered, and for the exemplary message MEET ME, the sequence will be as given in the following table.

Starting Clockwise to Up Down Cipher Position Character Pins Pins 9 5 TJ 13 5 G0 17 9 XX 7 8 EF 14 5 SK l3 5 FP Accordingly, the coded message to be transmitted to the receiver would be TJGOXXEF SKFP in the present instance. It is particularly interesting to note that with the present instrument, ciphers are not repeated when characters repeat in the clear text. Thus the first E is represented by the cipher GO while the second E is represented by XX and the third by FP." Likewise the two Ms are represented by different ciphers, and it should be apparent that usual cryptographic techniques are not applicable in attempted decoding of messages enciphered on instrument 10.

The receiver of the message will decipher it by repeating the procedure outlined above. That is, he first sets the primary and secondary keys into his instrument 10 and then rotates character disc 14 clockwise while watching for the first dual cipher TI to appear on cipher discs 16 and 18. When this cipher does appear, the parts will be in the configuration illustrated in FIGURE 3 with the M at the twelve oclock position on character disc 14. Continued clockwise rotation of character disc 14 in sequence will reveal the message. It should be noted that care must be taken not to pass a particular cipher since the sequence used to encipher the message must be used to decipher it.

The use of a dual character cipher and the use of a: continuing sequence of operation introduce other varia tions into the coding scheme which may be resorted to in order to further complicate the code if desired. For example, the characters on cipher disc 16 would normally be termed primary characters and would be transcribed first, as has been done in the above example, the primary T being set down before the secondary J in representing the clear M. A systematic transposition may be adopted however so that the secondary characters, on cipher disc 18, would be transcribed first in systematic fashion. The simplest system of this kind would be to transpose alternate ciphers so that the second, fourth, etc., ciphers would present the secondary character first. With this system, the above exemplary message would read TJOGXXFE SKPF.

Another possible variation is to introduce an additional rotation into character disc 14, that is to stop at the desired character only after a full 360 rotation of the character disc. Under this procedure, the exemplary message would read KSOGWYUP ZDDR. Still other variations are possible, and deciphering is easily accomplished as long as the receiver is aware of the system employed by the sender.

One other feature is worth mentioning and that is that additional characters may be employed on character disc 14 by placing them in an array spaced radially inwardly from the characters shown. Numerals and other symbols may be readily accommodated in this way. To designate which of the characters is intended then, the inner or outer one, the sender would transmit a prearranged signal, such as the letter combination QX after which the inner symbols would be used. A repetition of this signal would then indicate a return to the outer array of characters.

It should now be apparent that a cryptographic instrument has been described which adequately fulfills the objects of invention set forth hereinabove. Alterations and variations of the particular structure disclosed will occur to those skilled in the art and it is to be understood therefore that such changes may be resorted to without departing from the invention as it is defined in the appended claims.

I claim:

1. A cryptographic instrument comprising a base, first and second disc means rotatably mounted on said base, said first disc means having a plurality of pins mounted at selected positions about the periphery thereof, and said second disc means having a plurality of teeth thereon sequentially engageable by said pins whereby said second disc means will be incrementally rotated by said pins as said first disc means is rotated, said pins being movably mounted on said first disc means whereby the distribution of said pins may be changed;

(a) said first disc means comprising a character disc and said second disc means comprising a pair of cipher discs each having a plurality of teeth, said pins projecting selectively from opposite sides of said character disc and said cipher discs being disposed at opposite sides of said character disc whereby pins projecting from one side of said character disc will engage teeth on one of said cipher discs to rotate the same and pins projecting from the other side of said character disc will engage teeth on the other of said cipher discs to rotate the same.

2. A ciyptographic instrument as defined in claim 1 wherein said pins are slidably mounted in said character disc for protrusion selectively to the opposite sides thereof.

3. A cryptographic instrument as defined in claim 2 wherein said base is flat and said character disc and said cipher discs are mounted for rotation about axis normal to the plane of said base.

4. A cryptographic instrument as defined in claim 3, further comprising means in said base defining a recess underlying the periphery of said character disc whereby access may be had to pins protruding toward said base for pressing them to their other protruding position.

5. A cryptographic instrument as defined in claim 3, said cipher discs being mounted for rotation about a common axis.

6. A cryptographic instrument as defined in claim 5 wherein the cipher disc further from said base ha a transparent peripheral area, the cipher disc nearer said base carrying indicia viewable through said transparent area.

7. A cryptographic instrument as defined in claim 3 further comprising a pair of spaced parallel shafts extending from said base for mounting said character disc and said cipher discs, said cipher discs being mounted coaxially on one of said shafts, and spacer means engaging each of said discs for defining their respective axial positions on said shafts, including a spacer fixed to said one shaft between said cipher discs.

8. A cryptographic instrument as defined in claim 7 further comprising friction means on each of said spacer means for preventing free rotation of said character and cipher discs.

References Cited UNITED STATES PATENTS 1,073,585 9/1913 Beeman 40106.3 2,040,933 5/1936 Gillen 74-415 X 2,140,424 12/1938 Friedman 353 3,216,777 11/1965 Allen 74-415 X FOREIGN PATENTS 780,763 2/1935 France.

EUGENE R. CAPOZIO, Primary Examiner. R. WEIG, Assistant Examiner. 

